Homeless and runaway youth (HRY) are at a particularly high risk for HIV exposure due to their tendencies to engage in risky behaviors as a means of survival on their own. Despite their relatively high risk for exposure, little is known about the nature of and factors associated with these behaviors in this population. This grant application requests support for ad-year study to (a) examine the nature and extent of HRY's (aged 14 to 21) sexual behavior and use of alcohol and other drugs, as well as determine the relationship between the two groups of behaviors; and (b) identify factors in youth's social networks or "family of choice" networks while they are homeless (e.g., other homeless youth or adults, shelter operators, outreach workers) that may affect risk-taking behavior in this population. One wave of survey data will be collected from approximately 320 HRY found in shelters and soup kitchens in the District of Columbia (DC). The specific aims of the study are to: 1. determine the prevalences of alcohol and other drug use and high-risk sexual behavior among HRY; 2. determine the strength and nature of the correlation between alcohol and other drug use and high-risk sexual behavior among HRY; 3. determine the prevalence and characteristics (e.g., types of people, nature of relationships, level of closeness, longevity) of "family of choice" networks among HRY; and 4. focus on factors in a "family of choice" network that prevent or perhaps promote the occurrence of alcohol and other drug use and/or high- risk sexual behavior among HRY. This study will extend knowledge about HIV risk behaviors among HRY by (a) focusing on a relatively large sample of youth in a city (DC) who have not been similarly studied in such a large-scale effort; (b) including youth using soup kitchens in addition to shelter residents; (c) examining a wide range of risky behaviors and the relationship between them; (d) examining the characteristics of HRY's "family of choice" networks; and (e) exploring ways in which these networks may prevent or encourage risky behaviors.